She turned professional in 1996 at age 18 after graduating from high school, playing on both the Futures Tour and Players West Tour. In October 1996, she tied for sixth at the LPGA Final Qualifying Tournament to gain exempt status for 1997.[8] Her LPGA career started fairly slowly; she broke into the top fifty on the money list in her third season in 1999, but did not win until her sixth season. In 2002 she won her first LPGA event at the Longs Drugs Challenge in California. By 2004 she was one of the leading players on the tour, with three tournament victories, and a fifth-place finish on the money list. She won two tournaments in 2005 and moved up to third on the money list. She tied for second at the 2000 U.S. Women's Open, matched by her performance in the 2006 Women's British Open. Her first win of 2006 came at the Franklin American Mortgage Championship where she posted a tournament-record score of 19 under par. In 2006, she was the only American to win more than one event on the LPGA Tour, winning three times. She won the 2007 U.S. Women's Open, her first major championship. She was also a member of the United States Solheim Cup team in 2002,[9]2003,[10] and 2005.[11]

The hallmarks of Kerr's game are putting; she finished in the top five on the LPGA Tour in putts/greens hit in 2005 and 2006 and iron play. She was fifth in greens-in-regulation in 2005. In 2005, Kerr finished in the top 10 in half of the tournaments she entered, and ranked second in the LPGA in scoring average, trailing only Annika Sörenstam.

In 2010, Kerr won two of the first 10 tournaments on the LPGA Tour, including the LPGA Championship, which she won by a record-breaking 12-stroke margin over the second-place finisher Song-Hee Kim. As a result of this finish, she went to the top of the Women's World Golf Rankings on June 28, 2010.[12] Kerr held the position for three weeks before Ai Miyazato again regained the top ranking by a margin of 0.0006 average points.[13]

The LPGA and the Susan G. Komen Breast Cancer Foundation awarded Kerr the 2006 LPGA Komen Award[14] due to her dedication to find a cure for breast cancer through the foundation that she founded called Birdies for Breast Cancer. Kerr donates $50 per birdie. As of August 2009 she has raised over $750,000 through donations and an annual charity event.[15] Kerr created the foundation in honor of her mother, Linda, who has been her inspiration. The foundation was created in 2003, the year that her mother Linda was diagnosed with breast cancer.[14] Kerr also founded Curvature Wines, which helps to raise money for breast cancer charities. All Trump resorts carry the 2006 cabernet sauvignon under the Curvature Wines label.[16]

Kerr is 5 ft 3 in (1.60 m) in height. In 1999 she weighed 175 pounds (79 kg), a weight that caused her to have back spasms. Her parents, who are divorced, are both diabetics, and her mother had a heart attack when Kerr was in the ninth grade. After her weight peaked, Kerr began exercising regularly and went on a diet. By 2002, she had lost 50 pounds (23 kg), and weighs 125 pounds (57 kg).[17]

Kerr made an appearance on an episode of the third season of Donald Trump's television series The Apprentice in 2005. In 2006, Kerr married businessman Erik Stevens. Kerr and Stevens maintain a residence in Scottsdale, Arizona. One of her sponsors is Mutual of Omaha, which donates money to her breast cancer research foundation every time she places third or better.[18]

On December 8, 2013, Kerr and Stevens welcomed their first child, a son named Mason, via a surrogate.[19]

^ The Women's British Open replaced the du Maurier Classic as an LPGA major in 2001
^^ The Evian Championship was added as a major in 2013.LA = Low amateur
DNP = did not play
CUT = missed the half-way cut
WD = withdrew
T = tied
Green background for a win. Yellow background for a top-10 finish.